The invention relates to an arrangement for controlling a winch of a rock drilling equipment, the arrangement comprising a winch operated by a pressure fluid motor, a pump for operating the pressure fluid motor, a pressure-controlled pressure relief valve installed between pressure fluid channels of the pressure fluid motor for setting the counterpressure of the pressure fluid motor when pulling a wire off a wire drum, and control means for controlling the counterpressure of the pump.
In rock drilling equipments, typically in drill carriages, a winch is used when drilling on gradient planes, whereby the wire or cable of the winch is connected from its one end to the ground, usually to rock in such a manner that the equipment can be lowered on it down a slope and correspondingly, hauled back up after drilling is finished. In order that the equipment would stay put and there can be no sliding and sudden tightening of the wire and possible breaking as a result of it, the wire is always kept tight during driving in such a manner that the pressure of the pressure fluid affects the winching motor of the wire or that there is a pressure relief valve forming counterpressure between the pressure channels of the winching motor when releasing the wire. This kind of solution is disclosed in Finnish Published Specification 840,505. In the reference cited pressure fluid is supplied to the motor of the winch by means of a gear pump, the volume flow of the fluid produced by the pump being constant. Furthermore, the solution comprises a pressure relief valve connected between the pressure channels of the winching motor which valve is controlled by the pressure of the drive motor so that when driving down a slope the limiting pressure of the pressure limiter is lower than when reversing up the slope and spooling the wire at the same time. A problem of this solution is that the pump of the winch constantly produces pressure fluid that revolves in the pressure channel system of the winch. When spooling the wire off, both the pressure fluid flow produced by the motor and the pressure fluid flow from the pump have to be conducted through a pressure relief valve, whereby it is very difficult or practically impossible to adjust the tightness of the wire low enough. Moreover, the constant pressure fluid flow from the pump through the pressure relief valve to the container creates both energy loss and warmth, which needlessly strains the equipment. Further, when reversing the equipment, the operating speed of the winch cannot be adjusted as required, but when driving fast, the wire tends to slacken and go under the crawlers. Nor is it possible to adjust the tightness of the wire when reversing and spooling the wire.
The object of this invention is to provide an arrangement with which the adjustment of the tightness or tension of the wire and the spool speed or the spooling speed in both driving forwards and reversing is easily accomplished and easily adjusted.
The arrangement according to the invention is characterized in that the pump is a pressure-controlled volume flow pump and that the control means comprise an adjusting device with which the control pressure prevailing in the control channel of the pressure relief valve can be adjusted for setting the limit pressure and thus the counterpressure of the pressure fluid motor.
The essential idea of the invention is that a pressure-controlled volume flow pump is used for the pressure fluid pump of the winch and that it comprises an adjustment device which can be connected to control either the control pressure value of the pressure relief valve or the volume flow of the pressure fluid pump as required by the driving situation. An advantage of the arrangement according to the invention is that the tightness of the wire can be adjusted lower or higher in the desired manner when driving the equipment forwards, whereby the loading of the wire can be maintained suitable as required by the conditions. A further advantage is that when reversing, the volume flow of the pressure fluid pump and thus the speed of rotation of the winch can be adjusted, whereby the is force effective on the wire can be adjusted at the same time.
The invention will be explained in more detail in the accompanying drawings .